#include<iostream>
int main()
{
	double a,b,b1,c,c1,sum1,sum2,sum3,sum,i1,i2,i3;
	scanf("%lf%lf%lf",&a,&b,&c);
	for(i1=1;i1<=a;i1++)
		{
			sum1+=i1; 
		}
	for(i2=1;i2<=b;i2++)
		{
			b1=i2*i2;
			sum2+=b1;
		}
	for(i3=1;i3<=c;i3++)
		{
			c1=1/i3;
			sum3+=c1;
		}
	sum=sum1+sum2+sum3;
	printf("%.2lf\n",sum);
	system("pause");
	return 0;
}
